Jim - does the fabric on your eldorado have the fuzzy interior or is it the tricot? It has seemed to me that the 3-layer laminates, whether fuzzy or tricot, have superior breathability to the 2-layer ones, and that the fuzzy is the best. Why, I don't know. But it seems that way from my experience.
My experience in Goretex tents has not been what yours has, but then I've never had a Bibler. I made my own goretex tent once, and also tried an REI gretex tent many years ago when I was working there. Had condensation in both. I've also had condensation in conventional double-wall tents even without pitching the fly on the tent. So, single wall of fully breathable fabric - no coating or laminate at all, so one would expect even greater breathability than Goretex, - and yet I had condensation. So what to think? In other words, my experience has been that any fabric, breathable or not, can have condensation, and will if the interior humidity is high
I've been thinking of trying an experiment. I have a single-wall dome I made from coated nylon - have used it for snow camping for the last 15 years or so - and the coating is starting to fade. I made some stuffsacks from the same fabric, and I happened to wash one (it was my foodbag, and had gottten kinda grungy) - and the coating came completey off in the wash. Made me think about intentionally taking the coating off the dome for increased breathability and a little savings in weight. I never use it in the summer, just for snow camping. I've hesitated because it could rain on a backcountry ski trip - though I've never had it happen. But it would certainly be a good test of the relative merits of breathability, since it would be precisely the same shelter, first with and then without coating.

Fabric breathability is a weird thing. I have pants I made from EPIC frabic, and I love them- I find them very breathable and highly water repellent. I also have a BD Lighthouse tent, which I like so far for summer use. But I was interested to read this review:

http://pweb.jps.net/~prichins/tents.htm

Of the Lighthouse as a snow camping shelter. How the same fabric can seem so breathable in clothing and then get such bad condensation in a tent is confusing. Clearly the factors that affect whether a tent gets condensation are numerous